Thomas piarris



(No Model.) I l T. HARRIS.

GALVANOMETER.

No. 437,926. Patented Oct. 7, 1890.

UNITED STATES PATENT OFFICE.

THOMAS HARRIS, OF DETROIT, MICHIGAN, ASSIGNOR OF THREE-FOURTHS TO NATHAN T. THURBER, ALFRED LUGKING, AND HENRY F. DE B. CAM- ERON, OF SAME PLACE.

GALVANOM ETER.

SPECIFICATION forming part of Letters Patent No. 437,926, dated October '7, 1890. Application filed January 24, 1890- Serial No. 337,958. (No model.)

To all whom it may concern: In practice, the parts being arranged as de- Be it known that I, THOMAS HARRIS, a subscribed and shown, the instrument is so adject of the Queen of Great Britain, residing at justed that the magnetic filament points to 55 Detroit, in the county of Wayne and State of zero on the scale and that it hangs free to Michigan, have invented certain new and usemove in a vertical plane coincident with the ful Improvements in Instruments for Meascentral plane of the spool. The instrument uring Electric Currents, of which the followis now ready for use by connecting the elecing is a specification, reference being had trical source to be measured with the bind- 60 therein to the accompanying drawings. ing-posts F, so as to cause the current to be This invention relates to new and useful measured to flow through the solenoid. It improvements in devices for measuring elecwill be seen that whenever a current passes tric currents; and the invention consists in through the solenoid it must necessarily renthe peculiar construction and arrangement of der the iron filament D magnetic, even on the 6 3 parts, all as more fully hereinafter described, passage of a very feeble current, as the fiatand shown in the accompanying drawings, in tened form of the spool concentrates the elec- Whichtric field in which the filament is suspended.

Figure lis an elevation of adevice arranged At the same time, as the direction of the elecin accordance with my invention. Fig. 2 is trio current in passing through the solenoid a cross-section thereof on line 00 .r in Fig. 1, is not at right angles to the normal position 20 and Fig. 3 is a detached elevation of the of the magnetic filament, the latter, in accordpointer or index. ance with the law of Oersted, tends to move A is a solenoid provided with ahollow spool, into such position. This tendency, owing to preferably of brass or other suitable metal, the manner of suspending the filament, proand substantially of the wedge-shaped crossduces a deflection of the same from its nor- 2 5 section shown in Fig. 2. This is secured in mal position. The counteracting force, which a Vertical plane to a standard B in such a prevents the filament from being deflected manner that the winding is inclined to the until it stands at right angles to the direction horizontal, the drawing showing it at an angle of the current, is the force of gravitation 8c of about forty-five degrees. which tends to draw it back to the perpen- 0 Within the spool is suspended from a suitdicular. Thus between the two forces which able point of suspension 0 a magnetic filaact upon the filament the latter will be dement D, and below the spool is a graduated flected more or less, according to the strength are, which indicates electrical units, and the of the current. Thus with a suitable division zero-point of which coincides with the peron the scale the absolute or relative strength 35 pendicular position of the magnetic filament of different currents may be ascertained in when it is affected by gravity alone. units or degrees on the scale. In connect- F are the binding-posts to which the termiing the binding-posts to the electrical source nals of the solenoid are secured, and which to be measured the current flows through the 0 form the means of connecting the device with solenoid and forms an electrical field in which c the terminals of the electric source to be measthe pointer is free to move. Now it will be ured. seen that as the current traverses the solen- The magnetic filament is of soft iron, and old at an angle of about forty-five degrees preferably suspended by a filament G, of silk to the soft-iron section H of the pointer the or other matcriahto which its upper end is at latter in becoming magnetized will act in the 5 tached, while its lower end is extended by a same manner as the magnetic needle in Oerfilament I, of aluminium, cane, fiber, or other steds law-*that is, it moves in a direction light and non-magnetic material, and forming which will bring it at right angles to the dia suitable pointer to give accurate readings. rection of the currents. Owing to its manner The instrument is supported on a suitable of suspension it will thereby impart a move- 50 base,whichis preferablysupported on adjustment to the whole pointer around the point ing-screws to permit of adjusting the instru of suspension. At the same time this movement properly. ment carries it into the contracted portion of the solenoid, Where its distance from the current is reduced and the magnetic force thereby considerably increased. Thus while the pointer is moved out of the perpendicular position the force with which it is deflected or moved out of such position constantly increases, and may thus be made to form an offset to the increased force of gravity, which tends to return the pointer to normal. Thus it will be seen that with the proper proportions of the parts described the division on the scale which may represent any desired unit of measurement-such as amperes, volts, &c-can be made of practically-uniform sizes, thus giving for larger currents the same exact measurement as for smaller currents, which with the present measuring-instruments is not obtained.

The object of making the spool of the wedge-shaped cross-section shown is to increase the effective strength of the electric field with the-angle of deflection of the filament, for if this were not done it is obvious that the rapidly-increasing ratio with which the gravity resists the deflection of the filament would make the instrument less and less sensitive with the increase in the angle of deflection when larger currents have to be measured, and if the scale were graduated to indidicate units the divisions on the scale would become gradually smaller and smaller the fartherthey are from the zero-point. By deflecting the filament into an electrical field which increases the more it is deflected a compensating force is created, which increases the amplitude of deflection in any desired ratio, according to the degree or form of contraction of the spool and an instrument of this kind may thus be constructed in which the divi sions of the scale are uniform for like values from the zero-point to the highest point of measurement for which the particular instrument is adapted. 7

It will be seen that by making the filament substantially as described it is extremely light and sensitive, and by suspendingit from the higher corner of the spool with the solenoid so secured that the filament when at zero will hang diagonally across the spool, or nearly so, the largest sweep for the filament is obtained. 7 w

The number of windings-and kind of wire or conductor depends upon the kind of currents'to be measured, and as a matter of common knowledge need not be particularly described.

For the convenience of reading the scale the solenoid is so inclined that the filament has to move to the right, and it will be seen that it is immaterial in which direction it is traversed by the current to be measured.

In measuring instruments of this kind it is an important feature that it should readily respond to any variation of current and with out taking time by oscillating to and fro and thusmaking it difficult to obtain an. exact reading. This I have accomplished by using a very light needle of magn etic filament,which becomes highly saturated when between the metal plates forming the spool, and as it is well known that currents are set up which retard the motion producing them the filament will act with a dead beat.

The spirit of my invention consists in constructing a measuring-instrument in which the indications are a direct resultant of the well-known action of the magnetic needle toward electrical currents and of the gravity of the needle itself, and this is accomplished by means of a needle suspended on end.

What I claim as my invention is- 1. In an electrical measuring-instrument, the combination, with a coil, of a vertically-deflecting needle or filament suspended by a' flexible thread, substantially as described.

2. In an electrical measuring-instrnment,a vertically-deflecting needle or filament consisting of a magnetic section, a flexible thread by means of which it is vertically suspended, and a non-flexible lower extension of light and non-magnetic material, substantially as described.

3. In an electrical measuring-instrument,

the combination of a solenoid secured in a vertical plane with its winding at an angle to the horizontal and a vertically-deflecting needle or filament suspended therein on end by a flexible cord, substantially as described.

4. In an electrical measuring-instrument, the combination of an inclined wedge shaped solenoid and a magnetic filament vertically IOO suspended therein, substantially as described.

5. In an electrical measuring-instrument, the combination of an inclined solenoid wound upon a wedge-shaped spool and a vertically deflectingneedle or filament suspended therein, substantially as described.

6. The combination of a solenoid wound upon a wedge-shaped spool and secured at an incline in a vertical plane and a deflecting needle or filament suspended therein and con sisting of a soft-iron filament and a flexible thread secured thereto at one end and by means of which it is suspended, substantially as described.

7. In an electrical meaSuringinstrument, the combination of the solenoid secured in a vertical plane at an incline, the wedge shaped spool of metal upon which said solen oid is wound,adeflecting-filament suspended within said spool and consisting of a flexible thread, a magnetic or soft-iron portion secured to said thread, and a non-magnetic light extension forming a pointer at the lower end, substantially as described.

In testimony whereof I affix my signature, in presence of two witnesses, this 10th day of January, 1890.

, THOMAS HARRIS. Witnesses:

M. B. ODOGHERTY, GEO. O. GREGG. 

